Reaction accelerator for conductive polymer synthesis, conductive polymer and solid electrolytic capacitor

ABSTRACT

There is provided a reaction accelerator for polymerizing a conductive polymer, comprising: a salt of an anion derived from a sulfonic acid having a skeleton of benzene or naphthalene having at least one OH group, and at least one divalent or more cation other than a transition metal cation. There is also provided a conductive polymer including the salt concerning the reaction accelerator. There is also provided a solid electrolyte capacitor including the conductive polymer as a solid electrolyte. The conductive polymer has a high electric conductivity and good heat-resistance. The solid electrolyte capacitor is reliable for an extended period of time.

TECHNICAL FIELD

The present invention relates to a reaction accelerator used forsynthesizing a conductive polymer, a conductive polymer produced byusing the reaction accelerator, and a solid electrolytic capacitorincluding the conductive polymer as a solid electrolyte.

BACKGROUND ART

The solid electrolytic capacitor using the conductive polymer as a solidelectrolyte is less likely to ignite and has a low ESR (equivalentseries resistance), compared with conventional solid electrolyticcapacitors using manganese dioxide, a solid electrolyte. Thus, in viewof various excellent characteristics, the market has been expandedrapidly.

The conductive polymer as mentioned above is generally manufactured by achemical oxidative polymerization method. For example, a transitionmetal salt of an organic sulfonic acid such as iron p-toluenesulfonateis used as an oxidizer dopant solution, and a monomer such as thiopheneor its derivative is polymerized. See patent publications Nos. 1 and 2identified below.

Although this method was fit for mass production application, there wasa problem that the transition metal used as an oxidizer could remain inthe conductive polymer. Even if a washing process is performed in orderto remove the transition metal, the transition metal is one having acharacter which is difficult to be removed completely. Thus, there was arequest to improve the stability of a conductive polymer and a long-termreliability of a solid electrolytic capacitor by removing the influencesof the transition metal on the conductive polymer or on the solidelectrolyte capacitor in case where the transition metal remains in theconductive polymer. Therefore, there was a proposal to use an oxidizermade of one other than transition metal salts; i.e., peroxides, forexample. However, there was still a problem that compared with thetransition metal salts, the reactivity or the electric conductivity ofthe obtained conductive polymer was significantly low.

[Patent document 1]: Japanese Laid Open Patent Publication No. 10-50558,and [Patent document 2]: Japanese Laid Open Patent Publication2000-106331.

DISCLOSURE OF THE INVENTION Objective of the Invention

The present invention has been accomplished in view of the aboveproblems of the conventional technology. It promotes the syntheticreaction of a conductive polymer. There is provided a reactionaccelerator for preparing a conductive polymer while incorporating itinto the obtained conductive polymer, thereby improving the electricconductivity of the conductive polymer. There is also provided aconductive polymer obtained by using the reaction accelerator. There isfurther provided a solid electrolytic capacitor including the conductivepolymer as a solid electrolyte, which is reliable over a long period oftime.

Means for Solving the Objective

The inventors of the present invention have researched in order to solvethe objectives and found a reaction accelerator for preparing aconductive polymer. The reaction accelerator includes a salt of an anionderived from a sulfonic acid having a skeleton of benzene or naphthalenehaving at least one OH group, and at least one divalent or more cationother than a transition metal cation. Using the reaction accelerator, aconductive polymer is polymerized. It promotes the polymerizationreaction of the monomers for the conductive polymer, thereby resultingin efficient production of a conductive polymer with a good electricconductivity. Also, the conductive polymer is used as a solidelectrolyte to obtain a solid electrolytic capacitor which is reliableover a long period of time.

As stated above, the reaction accelerator for the conductive polymercomposition of the present invention is characterized in that itincludes a salt of an anion derived from a sulfonic acid having askeleton of benzene or naphthalene having at least one OH group, and atleast one divalent or more cation other than a transition metal cation.

Also, the conductive polymer of the present invention is characterizedin that it includes a salt of an anion derived from a sulfonic acidhaving a skeleton of benzene or naphthalene having at least one OHgroup, and at least one divalent or more cation other than a transitionmetal cation in a matrix of the conductive polymer.

Furthermore, the solid electrolytic capacitor of the present inventionis characterized in that it includes the conductive polymer of thepresent invention as a solid electrolyte.

EFFECT OF INVENTION

According to the present invention, there is provided a reactionaccelerator in which the polymerization reaction of the monomer can bepromoted in the process of preparing a conductive polymer. The electricconductivity of the conductive polymer can be maintained high. The solidelectrolytic capacitor can be reliable over a long period of time.

Namely, according to the present invention, a specific salt is used as areaction accelerator for obtaining a conductive polymer. The reactionaccelerator does not include a transition metal (transition metalcation) which causes acceleration of the degradation of the conductivepolymer. The salt concerned in the reaction accelerator is incorporatedinto the conductive polymer, thereby improving the electricconductivity, while efficiently polymerizing monomers. As results, aconductive polymer can be produced, which has a electric conductivityand an excellent heat resistance. Moreover, when using the conductivepolymer as a solid electrolyte, there is provided a solid electrolyticcapacitor reliable over a long period of time compared with conventionalones.

The conductive polymer of the present invention has a high electricconductivity and does not include a transition metal salt. Thus, a rapiddegradation caused by the transition metal salt does not occur in thepresent invention, though it was observed in conventional conductivepolymers. Therefore, it can be mainly used as a solid electrolyte of asolid electrolytic capacitor. Other than that, it can be also used ase.g., a cathode active material for batteries, an electrificationprevention sheet, an electrification prevention paint, anelectrification prevention agent such as an electrification preventionresin, and a corrosive proof agent such as a corrosion proof paint, inlight of the advantageous properties.

PREFERRED EMBODIMENTS OF THE INVENTION

The reaction accelerator for polymerizing a conductive polymer of thepresent invention (referred to as “reaction accelerator” hereafter)includes a salt of an anion derived from a sulfonic acid having askeleton of benzene or naphthalene having at least one OH group, and atleast one divalent or more cation (other than a transition metalcation).

The anion derived from a sulfonic acid having a skeleton of benzenehaving at least one OH group is an anion in which “H” (hydrogen) of asulfonate group of a sulfonic acid having a skeleton of benzene havingat least one OH group is eliminated. The anion derived from a sulfonicacid having a skeleton of naphthalene having at least one OH group is ananion in which “H” (hydrogen) of a sulfonate group of a sulfonic acidhaving a skeleton of naphthalene having at least one OH group iseliminated.

The anion derived from a sulfonic acid having a benzene or naphthaleneskeleton having at least one OH group can include ones derived fromacids selected from the group consisting of phenol sulfonic acid, phenoldisulfonic acid, cresol sulfonic acid, catechol sulfonic acid, dodecylphenol sulfonic acid, sulfosalicylic acid, naphthol sulfonic acid,naphthol disulfonic acid, and naphthol trisulfonic acid. Among them, ananion derived from phenol sulfonic acid or an anion derived from cresolsulfonic acid can be used in particular.

The salt of the reaction accelerator of the present invention includesthe anion as stated above and at least one divalent or more cation(other than a transition metal cation). The divalent or more cation isone which is divalent or more, including various inorganic cations andorganic cations other than transition metals. The above-mentionedinorganic cation can include magnesium ion (Mg²⁺), calcium ion (Ca²⁺),strontium ion (Sr²⁺), barium ion (Ba²⁺), radium ion (Ra²⁺), aluminum ion(Al³⁺), etc. In particular, calcium ion, strontium ion, barium ion andaluminum ion can be used. Also, the organic cation can include e.g.,ethylenediamine ion (⁺H₃NCH₂CH₂NH₃ ⁺), 1,3-propyldiamine ion(⁺H₃NCH₂CH₂CH₂NH₃ ⁺), and 1,2-propyldiamine ion [⁺H₃NCH₂CH(NH₃ ⁺)CH₃].In particular, ethylenediamine ion can be used.

The salt of the reaction accelerator is composed of the anion and thecation. There is no specific limination of the combination of the anionand the cation. The reaction accelerator can include a single salt, or acombination of two or more salts. Among the salts, phenolsulfonates suchas calcium phenolsulfonate, strontium phenolsulfonate, bariumphenolsulfonate, aluminum phenolsulfonate, ethylenediaminephenolsulfonate; and cresolsulfonates such as calcium cresolsulfonate,strontium cresolsulfonate, barium cresolsulfonate, aluminumcresolsulfonate, ethylenediamine cresolsulfonate can be particularlyused.

The reaction accelerator of the present invention can be in particularin a form of an aqueous solution in which the above-mentioned saltdissolves in water. Moreover, in order to improve permeability, a smallamount of an alcohol or a surface active agent can be added. Inaddition, the concentration of the above-mentioned salt can be 0.1 mol/lor more, or in particular, 0.5 mol/l or more, in case of a solution ofthe reaction accelerator. While mentioned later in detail, whenpreparing a conductive polymer using the reaction accelerator of thepresent invention, the above-mentioned salt regarding the reactionaccelerator is in advance applied to the surface of a base material(capacitor element etc.) in order to form a conductive polymer.Alternatively, it can be applied to the base material to which a monomerand/or oxidizer have been applied. For example, a base material (or abase material to which a monomer and/or an oxidizer has been applied)can be immersed into the reaction accelerator in the form of a solution.In that case, when the reaction accelerator of the present invention isprovided in a solution having the above-mentioned concentration, theoperation as described above can apply the salt in a sufficientquantity, thereby improving the productivity of the conductive polymer.In addition, the upper limit of the concentration of the salt in thesolution can be usually about 1 mol/l in view of the solubility of thesalt.

The method for preparing the salt is not particularly limited. Forexample, an aqueous solution including a sulfonic acid having a benzeneor naphthalene skeleton having at least one OH group can be neutralizedwith an alkali including a divalent or more cation other than atransition metal cation and an anion. Using such a process, a reactionaccelerator can be prepared directly in the form of an aqueous solution.Also, as described in the Examples later, the reaction acceleratorobtained as an aqueous solution form by the process above can besubjected to a process such as spray dry so as to isolate the salt,which can be then dissolved in water again to form a reactionaccelerator solution in the form of an aqueous solution. According tothis process, the concentration of the salt in the aqueous solution ofthe reaction accelerator can be more accurately adjusted.

The reaction accelerator in a state of an aqueous solution at aconcentration of 5 mass % can be in a condition with a pH value of 1 ormore, and in particular, of 4 or more. When the reaction accelerator isan aqueous solution having a pH value as explained above at theconcentration of 5 mass %, it can be particularly used in the productionof a conductive polymer for aluminum solid electrolytic capacitors.Also, the reaction accelerator in a state of an aqueous solution at aconcentration of 5 mass % can be in a condition of a pH of 10 or less,or in particular, of 8 or less. Thus, when producing the salt for thereaction accelerator by means of the neutralization method asabove-mentioned, the amounts of the acid and alkali added can beadjusted in order to meet the pH value of the aqueous solution of theobtained salts at the concentration of 5 mass %.

As to the salt concerning the reaction accelerator of the presentinvention, the anion of the salt is required to have at least one OHgroup. This is because OH group is considered to promote thepolymerization reaction of the monomers as well as contribute theimprovement of the conductivity of the obtained conductive polymer. Thereason is not be proved, but it is considered that proton of the OHgroup promptly proceeds with the polymerization reaction and is madeeasy to be incorporated in the conductive polymer. Also, the reason whythe anion of the salt is required to have a benzene or naphthaleneskeleton is because it can improve the heat resistance of the obtainedconductive polymer when the salt is incorporated therein.

Although the reason is not proved, the polymerization reaction ofmonomers can be promoted and the heat resistance of the conductivepolymer can be improved when using a divalent or more cation.

During polymerizing a conductive polymer, the reaction accelerator ofthe present invention can promote the polymerization reaction of themonomer, and can improve the productivity of the conductive polymer.Moreover, the salt for the reaction accelerator can be incorporated intothe produced conductive polymer as acid form to be served as a dopant.If it remains in the conductive polymer as salt form, it can contributeto the improvement of the electric conductivity of the conductivepolymer. Furthermore, the reaction accelerator of the present inventiondoes not include a transition metal. Thus, it does not affect theconductive polymer. Rather, the salt is incorporated into a conductivepolymer, thereby improving the heat resistance of the conductive polymeras explained above. Therefore, the conductive polymer obtained by usingthe reaction accelerator of the present invention become excellent inconductivity and heat resistance.

Namely, the conductive polymer of the present invention includes thesalt regarding the reaction accelerator in the matrix of the conductivepolymer. It can be particularly obtained by performing a chemicaloxidation polymerization of monomers using the reaction accelerator anda persulfate as an oxidizer.

In the conductive polymer of the present invention, the conductivepolymer serving as a matrix can be a polymer of at least one monomerselected from the group consisting of thiophene and its derivatives,pyrrole and its derivatives, and aniline and its derivatives.

The derivatives of thiophenes can include 3,4-ethylenedioxythiophene,3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene,3,4-alkylthiophene, 3,4-alkoxythiophene. The derivatives of pyrroles caninclude 3,4-alkylpyrrole, and 3,4-alkoxypyrrole. Furthermore, thederivatives of anilines can include 2-alkylaniline, and 2-alkoxyaniline.The carbon number of the derivatives of the alkyl group or the alkoxygroup in the derivatives of the thiophenes, the pyrroles and theanilines can be in particular 1 to 16.

Monomers in a liquid state can be used for polymerization as it is, butin order to advance the polymerization reaction more smoothly, themonomers can be diluted with an organic solvents such as methanol,ethanol, propanol, butanol, acetone, and acetonitrile, making it into asolution (an organic solution).

As a mode of the polymerization of the above-mentioned monomer, adifferent mode can be adopted depending on the type of application ofthe conductive polymer. For example, in a case where a conductivepolymer is made in a shape such as a film to incorporate it into anapplication device of the conductive polymer, any mode can be adopted.In a case where a conductive polymer is used as a solid electrolyte of asolid electrolytic capacitor, the manufacturing process of the solidelectrolytic capacitor can include the process in which the saltconcerning the reaction accelerator can be directly applied on thesurface of the capacitor element or in which the salt concerning thereaction accelerator can be applied after a monomer and/or an oxidizerhas been applied in advance. Then, the monomer is polymerized on thesurface of the capacitor element.

The example below is explained as to the polymerization process in orderto form a conductive polymer directly on the capacitor element of asolid electrolytic capacitor. A conductive polymer is formed by carryingout Process (A), Process (B), Process (C), and Process (D).

Process (A) [Application process of a reaction accelerator]: A capacitorelement is immersed in the reaction accelerator (which is usually in aform of a solution), or the reaction accelerator is applied on thecapacitor element, thereby making the reaction accelerator permeateinside fine holes of the capacitor element. Then, the salt is dried todeposit on the surface of the capacitor element. The capacitor elementcan be immersed in the reaction accelerator for a period of 1 second to5 minutes, for example. The capacitor element, which has been immersedor on which the reaction accelerator has been applied, can be dried at acondition of 20 to 100° C. for a period of 10 seconds to 10 minutes.

Process (B) (Application process of monomer): A monomer is diluted withan organic solvent to have a concentration of 5 to 100 mass %, and inparticular, of 10 to 40 mass % to obtain a monomer solution. Thecapacitor element, having deposited salt on the surface in Process (A),is immersed for a period of 1 second to 5 minutes, for example.

Process (C) (application process of oxidizer): The capacitor elementwhich is previously immersed into the monomer solution and taken outtherefrom is immersed into an oxidizer solution for a period of 1 secondto 5 minutes, for example, and then is taken out therefrom.

Process (D) (polymerization process): The capacitor element, on whichthe salt concerning a reaction accelerator, the monomer and the oxidizerare applied, is subjected to polymerization of the monomers at atemperature of 0 to 120° C., and in particular, 30 to 70° C., for aperiod of 1 minutes to 1 day, and in particular, 10 minutes to 2 hours.

Note that Process (A), Process (B), Process (C) and Process (D),respectively, can be carried out once to form a conductive polymer.However, note that each of these processes can be repeated several timesto form a conductive polymer. Moreover, the order of Process (A),Process (B) and Process (C) can be changed arbitrarily.

For example, in a case where a film-shaped conductive polymer is formed,a base material of a ceramic board and a glass board can be used insteadof a capacitor element. Other than that, the procedures similar toProcess (A), Process (B), Process (C) and Process (D) can be performedto form a conductive polymer on the surface of the base material. Then,the conductive polymer can be removed from the base material.

The oxidizer for the oxidizer solution in Process (C) can be inparticular persulfates, including sodium persulfate, barium persulfate,and organic persulfates (e.g., ammonium persulfate, alkylaminepersulfate, and imidazole persulfate). Among them, organic persulfatescan be especially used.

The alkylamine for the alkylamine persulfate can have an alkyl grouphaving a carbon number of 1 to 12. Examples can include ones same as“alkylamine salt of a sulfonic acid having a benzene or naphthaleneskeletone having at least one OH group and at least one sulfonate group”which are described later.

The imidazole salt constituting the imidazole persulfate can beimidazole per se or ones whose hydrogen atoms on the imidazole ringpartially substituted with an alkyl group or phenyl group having acarbon number of 1 to 20. That is, the imidazole persulfate includes notonly a salt of persulfate and imidazole but also a salt of persulfateand an imidazole derivative (e.g., an imidazole derivative in which somehydrogen atoms on the imidazole ring are substituted with an alkyl orphenyl group). The examples of persulfate imidazole (or imidazolederivatives) can include ones same as the “imidazole salt of a sulfonicacid having a benzene or naphthalene skeletone having at least one OHgroup and at least one sulfonate group” as mentioned later.

The persulfate can be usually used as a solution. The concentration ofthe persulfate in a solution can be more than 15 mass %, and inparticular, more than 20 mass %. The upper limit of the persulfateconcentration can be around 50 mass % in view of the solubility.

Also, in the process of preparing the conductive polymer, a solution ofthe following dopant for a conductive polymers can be used. The dopantsolution for a conductive polymers is a solution dissolving at least oneselected from the group consisting of alkylamine salts and imidazolesalts of a sulfonic acid having a benzene or naphthalene skeletonehaving at least one OH group and at least one sulfonate group at aconcentration of 40 mass % or more.

The above-mentioned dopant for conductive polymer, which is selectedfrom the group consisting of alkylamine salts and imidazole salts of asulfonic acid having a benzene or naphthalene skeletone having at leastone OH group and at least one sulfonate group, is incorporated into aconductive polymer to serve as a dopant. Therefore, when a dopantsolution for conductive polymer is used to produce a conductive polymer,the salt concerning the reaction accelerator serves as a dopant, as wellas the salt in the dopant solution for conductive polymer isincorporated in the conductive polymer, thereby further improving theconductivity of the conductive polymer. Also, by using the dopantsolution for conductive polymer, the polymerization reaction of amonomer can be further promoted.

Namely, the composition for polymerizing a conductive polymer includingthe reaction accelerator and the dopant solution for conductive polymerof the present invention can be separately packaged, for example. Usingthe composition to prepare a conductive polymer, the polymerizationreaction of a monomer can be improved further, while producing aconductive polymer having an excellent electric conductivity.

When a conductive polymer is produced by using the above-mentioneddopant solution for conductive polymer, a persulfate as an oxidizer canbe added into the dopant solution for conductive polymer to obtain anoxidizer dopant solution for conductive polymer. Thereby obtainedoxidizer dopant solution for conductive polymer can be substituted forthe oxidizer (persulfate) solution used in Process (C).

As the sulfonic acid having a benzene or naphthalene skeletone having atleast one OH group and at least one sulfonate group, the following canbe exemplified: e.g., phenol sulfonic acid, phenol disulfonic acid,cresol sulfonic acid, catechol sulfonic acid, dodecylphenol sulfonic,acid, sulfosalicylic acid, naphthol sulfonic, acid, naphthol disulfonicacid, and naphthol trisulfonic acid. The alkylamines constituting thealkylamine salts of the sulfonic acid having a benzene or naphthaleneskeletone can include an alkyl group having a carbon number of 1 to 12.Examples thereof can be methylamine, ethylamine, propylamine,butylamine, octylamine, dodecylamine, 3-ethoxypropylamine,3-(2-ethylhexyloxy)propylamine, etc.

Also, as the imidazole which constitutes imidazole salt of the sulfonicacid having a benzene or naphthalene skeletone, the following can beexemplified: imidazole per se and ones in which a part of hydrogen atomson the imidazole ring is substituted with an alkyl group or phenyl grouphaving a carbon number of 1 to 20. Namely, the term “imidazole salt of asulfonic acid having a benzene or naphthalene skeletone having at leastone OH group and at least one sulfonate group” can include a salt madeof an imidazole and a sulfonic acid having a benzene or naphthaleneskeletone having at least one OH group and at least one sulfonate group,as well as a salt made of an imidazole derivative and a sulfonic acidhaving a benzene or naphthalene skeletone having at least one OH groupand at least one sulfonate group. The imidazole derivative can includeones in which a part of hydrogen atoms on the imidazole ring issubstituted with an alkyl group or phenyl group.

Note that when the imidazole which constitutes imidazole salt of asulfonic acid having a benzene or naphthalene skeletone is substitutedwith an alkyl group or phenyl group having a carbon number of 1 to 20,the second and fourth positions of the imidazole ring can be substitutedin view of the production cost and good productivity.

Suitable examples of the imidazole to constitute the imidazole salt of asulfonic acid having a benzene or naphthalene skeletone can includeimidazole, 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole,2-butylimidazole, 2-undecylimidazole, 2-phenylimidazole,4-methylimidazole, 4-undecylimidazole, 4-phenylimidazole,2-ethyl-4-methylimidazole, and 1,2-dimethylimidazole. Among them,imidazole, 2-methylimidazole and 4-methylimidazole can be in particularused.

As a solvent of the above-mentioned dopant solution, it can be usuallygood with water, but an aqueous solution can be which includes anorganic solvent with a water affinity, such as ethanol, at anconcentration of around 50 volume % or less.

In case of an oxidizer dopant solution which is prepared by adding apersulfate into a dopant solution, as the concentration becomes higher,the synthetic reaction efficiency of the conductive polymer can beimproved, thereby allowing synthesis of the conductive polymer having ahigher electric conductivity. Therefore, as to at least one selectedfrom the group consisting of alkylamine salts and imidazole salts of asulfonic acid having a benzene or naphthalene skeletone having at leastone OH group and at least one sulfonate group, the concentration of thedopant solution can be 40 mass % or more, and in particular, 70 mass %or more. When the dopant solution has a high concentration as such, theoxidizer dopant solution having a high concentration can be prepared. Asto at least one selected from the group consisting of alkylamine saltsand imidazole salts of a sulfonic acid having a benzene or naphthaleneskeletone having at least one OH group and at least one sulfonate group,the upper limit of the concentration of the dopant solution can be 90mass %.

The pH of the dopant solution can be 1 or more, and in particular, 4 ormore. When producing a conductive polymer for an aluminum solidelectrolyte capacitor, the pH of the oxidizer dopant solution can be 1or more, thereby preventing the dissolution of the dielectric layer ofthe capacitor element pertaining to the aluminum solid electrolytecapacitor. By adjusting the pH of the dopant solution into 1 or more,there is provided an oxidizer dopant solution for preparing a conductivepolymer used for an aluminum solid electrolyte capacitor. Also, the pHof the dopant solution can be 10 or less, and in particular, 8 or less.

Also, an emulsifier can be added into the dopant solution. The additionof the emulsifier can provide a solution serving as an oxidizer dopantwhich promotes the polymerization reaction of a monomer more uniformly.Although various kinds of emulsifiers can be used, alkylamine oxide canbe especially used. The alkylamine oxide, even if remaining in theconductive polymer, does not remarkably reduce the electric conductivityof the conductive polymer. Also, when it is used as a solid electrolyteof a solid electrolyte capacitor, the alkylamine oxide does notremarkably reduce the function of the capacitor. The carbon number ofthe alkyl group of the alkylamine oxide can be 1 to 20. As thepolymerization reaction of the monomer proceeds, the pH of the reactionsystem is decreased. The alkylamine oxide can prevent the decrease ofthe pH.

As mentioned above, into the dopant solution for a conductive polymer apersulfate can be further added to be used as an oxidizer dopantsolution, which can be used for producing a conductive polymer. In thatcase, the concentration of the oxidizer dopant solution can affect theproductivity of the conductive polymer, i.e., the reactivity at the timeof polymerization of the monomer, resulting in affecting themanufacturing productivity and the characteristic, etc. Therefore, theconcentration of the oxidizer dopant in the solution can be 25 mass % ormore, and in particular, 30 mass % or more, and in more particular, 40mass % or more, and yet in more particular, 55 mass % or more. Also, itcan be 80 mass % or less.

Namely, if the concentration of the oxidizer dopant is too low, theeffect by using the oxidizer dopant solution can be less expected. Onthe other hand, the concentration of more than 25 mass % can promote thepolymerization reaction. The concentration of more than 30 mass % ormore than 40 mass % can satisfy the manufacture efficiency andproperties of the solid electrolyte capacitor (tantalum solidelectrolyte capacitor, niobium solid electrolyte capacitor and aluminumsolid electrolyte capacitor etc.), that is, the main application of theconductive polymer. The concentration of 55 mass % or more can bringfurther good results such as low ESR and high capacitance. However, ifthe concentration of the oxidizer dopant solution is higher than 80 mass%, the property can tend to decrease in turn. The concentration of theoxidizer dopant solution can be adjusted to be high as stated above. Useof such an oxidizer dopant solution and the reaction accelerator of thepresent invention will produce the conductive polymer, while improvingthe productivity of the conductive polymer as well as the manufacturingefficiency and properties of the solid electrolyte capacitor.

Moreover, the pH of the oxidizer dopant solution is important in case ofaluminum solid electrolyte capacitor, in particular. If the pH is lessthan 1, the dielectric layer can be dissolved, harming the properties.The pH of the oxidizer dopant solution thus can be 1 or more, and inparticular, 4 or more, but 10 or less, and in particular, 8 or less.Note that in case of producing a tantalum solid electrolyte capacitor,and a niobium solid electrolyte capacitor, etc., their dielectric layersare durable in acid resistance, so that the pH can be less than 1.

The pH of the reaction system becomes low as the polymerization reactionof the monomer progresses. However, when alkylamine oxide as mentionedabove is added into the oxidizer dopant solution as an emulsifier (forexample, when the oxidizer dopant solution is provided by using a dopantsolution including the emulsifier), the alkylamine oxide can serve aspreventing the decrease of the pH as well as proceeding with thepolymerization reaction uniformly.

While the concentration of the oxidizer dopant solution is explained inview of production of a solid electrolyte capacitor, the concentrationof the oxidizer dopant solution is also important when producing aconductive polymer. The concentration of the oxidizer dopant in thesolution can be 25 mass % or more, and in particular, 30 mass % or more,and more in particular, 55 mass % or more. Also, it can be 80 mass % orless.

Also, the mixing ratio of a persulfate with an alkylamine salt orimidazole salt of a sulfonic acid having a benzene or naphthaleneskeletone having at least one OH group and at least one sulfonate groupin the oxidizer dopant solution can be as follows: Per 1 mole of thealkylamine salt or imidazole salt of a sulfonic acid having a benzene ornaphthalene skeletone having at least one OH group and at least onesulfonate group, the persulfate can be added at 0.3 mol or more, and inparticular, 0.4 mol or more, but 2.0 mol or less, and in particular, 1.5mol or less. When the mixing ratio of the persulfate is more than theabove range, the ratio of the alkylamine salt or imidazole salt of thespecific organic sulfonic acid is decreased. As a result, the amount ofthe sulfuric acid ion as dopant is increased, thereby adverselyaffecting the improvement of the electric conductivity of the conductivepolymer by the oxidizer dopant solution. On the contrary, the mixingratio of the persulfate is less than the range as described above, itmay become difficult to produce a conductive polymer.

As with the conductive polymer of the present invention obtained asmentioned above, the content of the cation derived from the saltregarding the reaction accelerator (that is, a divalent or more cationother than a transition metal cation) in the entire conductive polymercan be 10 ppm or more, and in particular, 20 ppm or more, and more inparticular, 50 ppm or more. When the conductive polymer includes thedivalent or more cation at the content stated above, better heatresistance can be obtained. Also, the upper limit of the divalent ormore cation in the conductive polymer is not limited, but usually, itcan be about 5000 ppm, and in particular, 1000 ppm, and more inparticular, 500 ppm, and yet more in particular, 300 ppm or less. Inview of balancing the advantageous effects by using the reactionaccelerator (especially, the improvement of heat-resistant) and theeconomically disadvantageous effects by using a large amount of thereaction accelerator, the content of the divalent or more cation in theentire conductive polymer can be 10 ppm or more, and in particular, 20ppm or more, and more in particular, 50 ppm or more, but 1000 ppm orless, and in particular, 500 ppm or less, and more in particular, 300ppm or less. The content of the divalent or more cation in theconductive polymer can be measured by the method shown explained later.

The solid electrolyte capacitor of the present invention can use theconductive polymer of the present invention as a solid electrolyte.Other components can be similar to those used in conventional solidelectrolyte capacitors. Various solid electrolyte capacitor can beprepared by selecting the material for the capacitor element such asaluminum solid electrolyte capacitor, niobium solid electrolytecapacitor and tantalum capacitor.

EXAMPLES

The present invention is described in detail hereafter based onexamples. However, the following description of the examples does notrestrict the present invention. Without departing from the scopeinferred in the context, a modification is included in the presentinvention. In the following examples, the term “%” for the concentrationof a solution, diluted solution, or dispersion solution, etc. means“mass %” unless otherwise stated.

First, synthesis examples of phenolsulfonate and cresolsulfonate aredisclosed. They are used as a reaction accelerator in the examples.

Synthesis Example 1 Synthesis of Calcium Phenolsulfonate and Preparationof its Aqueous Solution

While 1000 g of a phenol sulfonic acid aqueous solution at aconcentration of 5% was stirred at room temperature, calcium hydroxidewas gradually added to reach a pH of about 6. The mixture wascontinuously stirred for a while. Then, this was filtered with 0.4micrometer glass filter to obtain a calcium phenolsulfonate aqueoussolution, which was then spray-dried to obtain powders of calciumphenolsulfonate.

Thereby obtained calcium phenolsulfonate is dissolved in pure water tobecome a concentration of 0.5 mol/l, which was then filtered with 0.2micrometer filter to obtain an aqueous solution.

Synthesis Example 2 Synthesis of Strontium Phenolsulfonate, andPreparation of an Aqueous Solution

Instead of using calcium hydroxide, strontium hydroxide was added in thesame manner as Synthesis Example 1 so as to produce strontiumphenolsulfonate. A solution thereof having a concentration of 0.5 mol/lwas obtained.

Synthesis Example 3 Synthesis of Barium Phenolsulfonate, and Preparationof an Aqueous Solution

Instead of using calcium hydroxide, barium hydroxide was added in thesame manner as Synthesis Example 1 so as to produce bariumphenolsulfonate. A solution thereof having a concentration of 0.5 mol/lwas obtained.

Synthesis Example 4 Synthesis of Calcium Cresolsulfonate, andPreparation of an Aqueous Solution

Instead of using the phenol sulfonic acid solution, a cresol sulfonicacid solution was used in the same manner as Synthesis Example 1 so asto produce calcium cresolsulfonate. A solution thereof having aconcentration of the 0.5 mol/l was obtained.

Synthesis Example 5 Synthesis of Ethylenediamine Phenolsulfonate, andPreparation of an Aqueous Solution

Instead of using calcium hydroxide, ethylenediamine was added in thesame manner as Synthesis Example 1 so as to produce ethylenediaminephenolsulfonate. A solution thereof having a concentration of 0.5 mol/lwas obtained.

Synthesis Example 6 Synthesis of Ethylenediamine Sulfonate andPreparation of an Aqueous Solution of an Ethylenediamine PolystyrenePhenolsulfonate

1000 g of 5% phenol sulfonic acid solution was stirred at roomtemperature, while ethylenediamine was added slowly until the pH becameabout 6. The stirring was continued for a while. Then, this was filteredwith 0.4 micrometer glass filter, so as to obtain an ethylenediaminephenolsulfonate solution, which was then spray-dried to obtain powdersof ethylenediamine phenolsulfonate.

Then, 20% polystyrene sulfonic acid aqueous solution was stirred at roomtemperature while ethylenediamine was slowly added until a pH becomesabout 5. Water was added to adjust a solution having a concentration of20%. Into the mixture, the powders of the ethylenediaminephenolsulfonate were dissolved. Accordingly, a solution (pH 5), in which0.5 mol/l of ethylenediamine phenolsulfonate was dissolved into 20%ethylenediamine polystyrene phenolsulfonate aqueous solution, wasobtained.

Synthesis Example 7 Synthesis of Ethylenediamine Sulfonate andPreparation of a Solution of an Ethylenediamine PolystyrenePhenolsulfonate

1000 g of 5% phenol sulfonic acid solution was stirred at roomtemperature, while ethylenediamine was added slowly until the pH becameabout 1.5. The stirring was continued for a while. Then, this wasfiltered with 0.4 micrometer glass filter, so as to obtain anethylenediamine phenolsulfonate solution, which was then spray-dried toobtain powders of ethylenediamine phenolsulfonate.

Then, 5% polystyrene sulfonic acid aqueous solution was stirred at roomtemperature while ethylenediamine was slowly added until a pH becomesabout 1.5 and adjusted by distillation to a solution having aconcentration of 20%. Into the solution, the powders of theethylenediamine phenolsulfonate were dissolved. Accordingly, a solution(pH 1.5), in which 0.5 mol/l of ethylenediamine phenolsulfonate wasdissolved into 20% ethylenediamine polystyrene phenolsulfonate aqueoussolution, was obtained.

Synthesis Example 8 Synthesis of Aluminum Phenolsulfonate and an AqueousSolution Thereof

Into 1000 g of 10% aluminum sulfate solution, 2N sodium hydroxidesolution was added to adjust it into a pH of 7.6. The precipitates bythis operation were collected by filtering them with 4 micrometerfilter, and then dispersed into 1000 ml of pure water while stirring for10 minutes. The precipitates were again collected by 4 micrometerfilter. The process of the dispersion and the filtering was repeatedthree times. Then, the precipitates as collected was dispersed into 800ml of pure water, into which 281 g of phenol sulfonic acid was added,while stirring it at room temperature for 15 hours. Then, the insolublematter was removed with 0.4 micrometer filter, so as to obtain asolution of aluminum phenolsulfonate. By spray drying the solution,powders of aluminum phenolsulfonate was obtained.

Thereby obtained aluminum phenolsulfonate was dissolved in pure watersuch that its concentration became 0.5 mol/l, which was subject to 0.2micrometer filter to obtain an aqueous solution.

Evaluation in Conductive Polymer Example 1

A heat-resistant tape (2 mm in width) was stuck on a ceramic plate (40mm in length and 3.3 mm in the width) in the transverse directionthereof such that the heat-resistant tape divides into a portion having30 mm in size from one end of the lengthwise direction and anotherportion having a size of 10 mm from the other end of the lengthwisedirection. Then, the portion having 30 mm in size extending from the oneend of the lengthwise direction of the ceramic plate to theheat-resistant tape (29 mm×3.3 mm) was immersed into the 0.5 mol/lcalcium phenolsulfonate solution (pH 6.0) prepared in Synthesis Example1 for 1 minute. Then, the ceramic plate was taken out to place it into adrier at a temperature of 100° C. for 5 minutes. 35% ethanol solution of3,4-ethylenedioxythiophene was prepared in advance, into which theportion of the ceramic plate where it was immersed into the calciumphenolsulfonate solution and dried in the drier was immersed at thedepth of the heat-resistant tape for a period of 1 minute. Then, theceramic plate was immersed into 45% ammonium persulfate aqueous solutionfor 10 seconds. A polymerization process was done for 40 minutes at roomtemperature to form a conductive polymer film. Then, the ceramic platewhose surface was partly covered with the conductive polymer film wasimmersed into pure water for 30 minutes, and it was taken out for dryingit for 30 minutes at 70° C.

The series of the process from the step of immersing the ceramic plateinto the calcium phenolsulfonate aqueous solution to the step of dryingit at 70° C. for 30 minutes was repeated four times. Thereafter, theceramic plate was dried at 150° C. for 60 minutes. Then, a load of 5 tonwas applied for 5 minutes on the ceramic plate to equalize the thicknessof the conductive polymer film.

Example 2

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,the 0.5 mol/l strontium phenolsulfonate aqueous solution (pH 6.0) asprepared in Synthesis Example 2 was used. Other than that, the sameprocedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Example 3

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,the 0.5 mol/l aluminum phenolsulfonate aqueous solution (pH 6.0) asprepared in Synthesis Example 8 was used. Other than that, the sameprocedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Example 4

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,the 0.5 mol/l calcium cresolsulfonate aqueous solution (pH 6.0) asprepared in Synthesis Example 4 was used. Other than that, the sameprocedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Example 5

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,the 0.5 mol/l ethylenediamine phenolsulfonate aqueous solution (pH 5.0)as prepared in Synthesis Example 5 was used and the aqueous solution waskept at 60° C. Other than that, the same procedures as Example 1 wereperformed so as to obtain a conductive polymer film formed on thesurface of the ceramic plate.

Example 6

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,a solution (pH 5), in which 0.5 mol/l of ethylenediamine phenolsulfonatewas dissolved into 20% ethylenediamine polystyrene phenolsulfonateaqueous solution as prepared in Synthesis Example 6, was used and theaqueous solution was kept at 60° C. Other than that, the same proceduresas Example 1 were performed so as to obtain a conductive polymer filmformed on the surface of the ceramic plate.

Example 7

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,a solution (pH 1.5 when diluted into a concentration of 5%), in which0.5 mol/l of ethylenediamine phenolsulfonate was dissolved into 20%ethylenediamine polystyrene phenolsulfonate aqueous solution as preparedin Synthesis Example 7, was used and the aqueous solution was kept at60° C. Other than that, the same procedures as Example 1 were performedso as to obtain a conductive polymer film formed on the surface of theceramic plate.

Example 8

Instead of using the 45% ammonium persulfate, an oxidizer dopantsolution in which 40% ammonium persulfate was mixed with 70%2-methylimidazole phenolsulfonate aqueous solution (pH 5.0) at a volumeratio of 1:1 was used. Other than that, the same procedures as Example 1were performed so as to obtain a conductive polymer film formed on thesurface of the ceramic plate.

Example 9

Instead of using the 45% ammonium persulfate, an oxidizer dopantsolution in which 40% ammonium persulfate was mixed with 70%2-methylimidazole phenolsulfonate aqueous solution (pH 5.0) at a volumeratio of 1:1 with further addition of decyldimethylamineoxide at aconcentraton of 0.2% was used. Other than that, the same procedures asExample 1 were performed so as to obtain a conductive polymer filmformed on the surface of the ceramic plate.

Example 10

Instead of using the 45% ammonium persulfate, an oxidizer dopantsolution in which 40% ammonium persulfate was mixed with 70%4-methylimidazole phenolsulfonate aqueous solution (pH 5.0) at a volumeratio of 1:1 with further addition of decyldimethylamineoxide at aconcentraton of 0.2% was used. Other than that, the same procedures asExample 1 were performed so as to obtain a conductive polymer filmformed on the surface of the ceramic plate.

Comparative Example 1

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, 0.5mol/l sodium phenolsulfonate aqueous solution (pH 6.0) was used. Insteadof repeating the polymerization process four times, the polymerizationwas repeated six times. Other than the differences, the same proceduresas Example 1 were performed so as to obtain a conductive polymer filmformed on the surface of the ceramic plate.

Comparative Example 2

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, 0.5mol/l ammonium phenolsulfonate aqueous solution (pH 6.0) was used.Instead of repeating the polymerization process four times, thepolymerization was repeated six times. Other than the differences, thesame procedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Comparative Example 3

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, 0.5mol/l calcium m-xylenesulfonate aqueous solution (pH 6.0) was used.Instead of repeating the polymerization process four times, thepolymerization was repeated six times. Other than the differences, thesame procedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Comparative Example 4

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, 0.5mol/l sodium m-xylenesulfonate aqueous solution (pH 6.0) was used.Instead of repeating the polymerization process four times, thepolymerization was repeated six times. Other than the differences, thesame procedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Comparative Example 5

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, 0.5mol/l sodium butylnaphthalenesulfonate aqueous solution (pH 6.0) wasused. Instead of repeating the polymerization process four times, thepolymerization was repeated six times. Other than the differences, thesame procedures as Example 1 were performed so as to obtain a conductivepolymer film formed on the surface of the ceramic plate.

Comparative Example 6

40% butanol solution of ferric p-toluenesulfonate was mixed with3,4-ethylenedioxythiophene at a mass ratio of 4:1, and the mixture wasstrongly shaken for 10 seconds. Into this mixture, the same ceramicplate as used in Example 1 was quickly immersed for 5 seconds, which wasthen taken out. The ceramic plate was kept for 30 minutes at roomtemperature and then it was immersed in pure water for 30 minutes. Then,the ceramic plate was taken out and dried for 30 minutes at 50° C.

The series of the process from the step of immersing the ceramic plateinto the mixture of the ferric p-toluenesulfonate butanol solution and3,4-ethylenedioxythiophene to the step of drying at 50° C. for 30minutes was repeated five times to form a conductive polymer film on thesurface of the ceramic plate. The subsequent procedures were the same asExample 1.

The electric conductivities of the conductive polymer films of Examples1 to 10 and Comparative Examples 1 to 6 were measured in accordance withJIS K 7194 using a four probes electricity measurement instrument[MCP-T600 (brand name) by Mitsubishi Chemical Corporation]. The valuesobtained thereby are listed as “Initial Conductivity” in Table 1. Theresults in Table 1 were obtained by measuring the conductivity at fivepoints of each conductive polymer film, from which an averaged value wascalculated with rounding off the decimal points.

Also, after measuring the electric conductivity, the conductive polymerfilm on the ceramic plate was kept in a constant temperature bath at150° C. for 100 hours, and then taken out. Then, the electricconductivity of the conductive polymer film was measured in the same wayas described above. The results are listed in Table 1 as “ElectricConductivity after 100 Hour Storage at 150° C.”

TABLE 1 Initial Electric Electric Conductivity after Conductivity 100Hour Storage at 150° C. (S/cm) (S/cm) Example 1 68 45 Example 2 66 43Example 3 62 40 Example 4 59 40 Example 5 70 47 Example 6 71 48 Example7 78 49 Example 8 75 55 Example 9 87 64 Example 10 88 66 ComparativeExample 1 57 21 Comparative Example 2 56 19 Comparative Example 3 41 1Comparative Example 4 38 0.9 Comparative Example 5 (*1) (*1) ComparativeExample 6 60 1 Note that the mark (*1) in Table 1 indicates that aconductive polymer film on the surface of the ceramic plate was notobtained in a good condition so that its electric conductivity was notmeasured.

As understood from the results in Table 1, the conductive polymers ofExamples 1 to 10 were more excellent in electric conductivity than thoseof Comparative Examples 3 and 4, and more excellent in heat resistancethan those of Comparative Examples 1 to 6.

Note that in Comparative Examples 1 to 5, the polymerization process wasrepeated four times at first. However, since a conductive polymer wasnot formed on the given portion of the ceramic plate, the polymerizationwas further repeated two times. As results, a conductive polymer filmwas finally formed entirely at the given portions of the ceramic platein Comparative Examples 1 to 4. However, a conductive polymer film stillcould not be formed in Comparative Example 5. On the contrary, fewerrepetition of the polymerization process could form good conductivepolymer films in Examples 1 to 10. The results show that the reactivityof 3,4-ethylenedioxy thiophene, a monomer, was promoted by the reactionaccelerator containing a salt of an anion derived from phenol sulfonicacid or cresol sulfonic acid and a divalent or more cation other than atransition metal cation.

Moreover, the results in Example 1 and 8 to 10 using the same reactionaccelerator, that is, calcium phenolsulfonate, are compared as follow:In Examples 8 to 10, instead of using an ammonium persulfate solution asan oxidizer solution, an oxidizer dopant solution including a conductivepolymer polymerization dopant such as 2-methylimidazole phenolsulfonateor 4-methylimidazole phenolsulfonate was used. The conductive polymersin Examples 8-10 were better in characteristics than that in Example 1in which 3,4-ethylenedioxythiophene was polymerized in an oxidizersolution without the dopant. The effects by using the reactionaccelerator together with the oxidizer dopant solution including adopant were proven. Further, in Examples 9 and 10, the dopant solution(or oxidizer dopant solution) containing decyldimethylamineoxide, anemulsifier was used. Compared with Example 8 not including such anemulsifier, the conductive polymers of Examples 9 and 10 were better incharacteristics.

Next, the conductive polymer film of Example 1 was removed from theceramic plate, 100 mg of which was put into a 50 ml vial with anairtight stopper. Then, 2 ml of sulfuric acid was added in it and keptat 50° C. for one day. Then, it diluted with water and was subjected tofiltering. ICP measurement was performed to the solution. The amount ofcalcium ions in the conductive polymer was measured by using acalibration curve. It was measured as 103 ppm.

Also, the amount of ions in the conductive polymers of the conductivepolymer films produced in accordance with Examples 2, 5, and 8 andComparative Examples 1 and 3 was measured. Strontium ion was 68 ppm inExample 2; ethylenediamine ion was 60 ppm in Example 5; calcium ion was65 ppm in Example 8; sodium ion was 4 ppm in Comparative Example 1; andcalcium ion was 100 ppm in Comparative Examples 3. Furthermore, withrespect to the conductive polymer film of Comparative Example 2, thesame procedure as Example 1 was performed to prepare a solution tomeasure ammonium ion by ion chromatography, using the calibration curve.The concentration was 2 ppm.

The conductive polymer of Example 1 used calcium being a divalentcation, whereas the conductive polymer of Comparative Example 1 usedsodium being a monovalent cation. Other than that, Example 1 was thesame as Comparative Example 1. It is considered that the results listedin Table 1 show that the divalent or more cation as a reactionaccelerator contributed has furthered improvement of the heat-resistantof the conductive polymer.

Also, the conductive polymer of Example 1 was different from that ofComparative Example 3 only in the anions concerning the reactionaccelerators. It is considered that the results listed in Table 1 showthat the anion concerning the reaction accelerator, derived from asulfonic acid having a benzene skeleton containing at least one OHgroup, contributed to improve the initial characteristic (initialelectric conductivity) and the heat-resistant (electric conductivityafter storage) of the conductive polymer.

Evaluation Using an Aluminum Solid Electrolyte Capacitor Example 11

An aluminum etched foil having a size of 10 mm in length and 3.3 mm inwidth was provided. A polyimide solution was applied to the transversedirection of the above-mentioned foil to have a width of 1 mm in such away that a portion with 4 mm in size extended from one end of thelengthwise direction was divided from another portion with 5 mm in sizeextended from the other end. Then, the foil was dried. Then, a silverwire was attached as a positive electrode at the portion to have a sizeof 2 mm spaced from the end, which is located in said portion with 5 mmin size from the other end. The portion with 4 mm in size from one endof the lengthwise direction (4 mm×3.3 mm) was immersed into 10% adipicacid ammonium aqueous solution, while applying a voltage of 13V forchemical conversion treatment to form a dielectric coating so as toproduce a capacitor element.

Next, into the 0.5 mol/l calcium phenolsulfonate aqueous solution (pH6.0) prepared in accordance with Synthesis Example 1, the portion inwhich the dielectric coating was formed was immersed at the depth of theportion where the polyimide solution was applied. One minute later, itwas taken out to place it into a drier at 100° C. for 5 minutes. Then,it was taken out from the drier. Then, the portion of the capacitorelement, where it was immersed into the calcium phenolsulfonate aqueoussolution, was immersed into a 35% 3,4-ethylenedioxythiophene ethanolsolution which was prepared in advance, in such a manner that it isimmersed at the depth of the portion where the polyimide solution wasapplied. It was taken out one minute later. Then, the capacitor elementwas immersed into a 45% ammonium persulfate aqueous solution for tenseconds, and then it was taken out and dried for 40 minutes at roomtemperature in order to polymerize to form a conductive polymer layer.Then, the capacitor element, a part of which surface is coated with aconductive polymer layer, was immersed into pure water for 30 minutes.It was then taken out to be dried at 70° C. for 30 minutes.

A series of processes from the step of immersing the capacitor elementinto the calcium phenolsulfonate aqueous solution to the step of dryingit at 70° C. for 30 minutes was repeated eight times. Then, thecapacitor element was dried at 150° C. for 60 minutes. Then, theconductive polymer layer was covered with a carbon paste and a silverpaste such that a silver wire as a negative electrode was provided at aportion 3 mm distanced from the end of the lengthwise direction.Furthermore, the exterior was coated with an epoxy resin, and an agingprocess was performed so as to obtain an aluminum solid electrolytecapacitor.

Example 12

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solutionin Example 11, the 0.5 mol/l strontium phenolsulfonate aqueous solution(pH 6.0) prepared in accordance with Synthesis Example 2 was used. Otherthan that, the same procedure used in Example 11 was used to produce analuminum solid electrolyte capacitor in this example.

Example 13

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solutionin Example 11, the 0.5 mol/l calcium cresolsulfonate aqueous solution(pH 6.0) prepared in accordance with Synthesis Example 4 was used. Otherthan that, the same procedure used in Example 11 was used to produce analuminum solid electrolyte capacitor in this example.

Example 14

Instead of using the 45% ammonium persulfate aqueous solution, anoxidizer dopant solution was used. The oxidizer dopant solution in thisExample was prepared as follows: 40% ammonium persulfate aqueoussolution and 70% 2-methylimidazole phenolsulfonate aqueous solution weremixed together at a volume ratio of 1:1, into whichlauryldimethylamineoxide was further added such that it was included ata concentration of 0.1%. Instead of repeating the polymerization processeight times, it was repeated five times in this example. Other than thedifferences, the same procedure used in Example 11 was used to producean aluminum solid electrolyte capacitor in this example.

Comparative Example 7

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 11, 0.5 mol/l sodium phenolsulfonate aqueous solution (pH 6.0)was used. Other than that, the same procedure used in Example 11 wasused to produce an aluminum solid electrolyte capacitor in this example.

Comparative Example 8

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 11, 0.5 mol/l ammonium phenolsulfonate aqueous solution (pH 6.0)was used. Other than that, the same procedure used in Example 11 wasused to produce an aluminum solid electrolyte capacitor in this example.

Comparative Example 9

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 11, 0.5 mol/l calcium m-xylenesulfonate aqueous solution (pH6.0) was used. Other than that, the same procedure used in Example 11was used to produce an aluminum solid electrolyte capacitor in thisexample.

Comparative Example 10

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 11, 0.5 mol/l magnesium m-xylenesulfonate aqueous solution (pH6.0) was used. Other than that, the same procedure used in Example 11was used to produce an aluminum solid electrolyte capacitor in thisexample.

Comparative Example 11

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 11, 0.5 mol/1 magnesium butylnaphthalenesulfonate aqueoussolution (pH 6.0) was used. Other than that, the same procedure used inExample 11 was used to produce an aluminum solid electrolyte capacitorin this example.

Comparative Example 12

40% ferric p-toluenesulfonate butanol solution and3,4-ethylenedioxythiophene were mixed together at a mass ratio of 4:1,and the mixture was strongly shaken for 10 seconds. Then, into themixture, the same capacitor element used in Example 11 was quicklyimmersed, and 5 seconds later, it was taken out. The capacitor elementwas kept at room temperature for 30 minutes, and it was immersed in purewater for 30 minutes. Then, the capacitor element was taken out to bedried at 50° C. for 30 minutes.

A series of the processes from the step of immersing the capacitorelement into the mixture of ferric p-toluenesulfonate butanol solutionand 3,4-ethylenedioxythiophene to the step of drying it at 50° C. for 30minutes was repeated five times so as to form a conductive polymer layerpartially on the surface of the capacitor element. Then, the capacitorelement was dried at 150° C. for 60 minutes. Then, the conductivepolymer layer was coated with carbon paste and a silver paste, and asilver wire as a negative electrode was provided at a portion 3 mmdistanced from the end of the lengthwise direction. The exterior wascoated with an epoxy resin, and an aging process was performed so as toproduce an aluminum solid electrolyte capacitor.

As to the aluminum solid electrolyte capacitor of Examples 11 to 14 andComparative Examples 7 to 12, capacitance and ESR (equivalent seriesresistance) were measured. The results are shown in Table 2. The resultsin Table 2 were obtained as follows: each of capacitance and ESR wasmeasured at 10 points, from which an averaged value was calculated whilerounding off the decimal points.

Capacitance: Capacitance was measured by using LCR tester manufacturedby HEWLETT PACKARD Company (4284A) at a condition of 25° C. and 120 Hz.

ESR: ESR was measured by using LCR tester manufactured by HEWLETTPACKARD Company (4284A) at a condition of 25° C. and 100 kHz.

TABLE 2 Capacitance (μF) ESR (mΩ) Example 11 9.8 14 Example 12 9.9 13Example 13 9.8 13 Example 14 9.9 12 Comparative Example 7 (*2) (*2)Comparative Example 8 (*2) (*2) Comparative Example 9 (*2) (*2)Comparative Example 10 (*2) (*2) Comparative Example 11 (*2) (*2)Comparative Example 12 9.8 14 Note that in Table 2, the mark (*2)indicates that the conductive polymer layer could not coat the whole ofthe portion where the conductive polymer layer should have been formed,and capacitance and ESR were not measured.

Five samples were arbitrarily selected from good samples of the aluminumsolid electrolyte capacitors of Examples 11 to 14 and ComparativeExample 12. They were kept at 125° C. for 500 hours, and then,capacitance and ESR were measured in the same manner as described above.The results are listed in Table 3 below. The results in Table 3 wereobtained as follows: each of capacitance and ESR was measured at 5points, from which an averaged value was calculated while rounding offthe decimal points.

TABLE 3 Capacitance (μF) ESR (mΩ) Example 11 9.6 15 Example 12 9.8 14Example 13 9.6 14 Example 14 9.7 13 Comparative Example 12 9.6 49

Furthermore, another sets of five samples were arbitrarily selected fromgood samples of the aluminum solid electrolyte capacitors of Examples 11to 14 and Comparative Example 12. They were kept at an environment of85° C. and 85% RH for 1000 hours, and then capacitance and ESR weremeasured in the same manner as described above. The results are listedin Table 4 below. The results in Table 4 were obtained as follows: eachof capacitance and ESR was measured at 5 points, from which an averagedvalue was calculated with rounding off the decimal points.

TABLE 4 Capacitance (μF) ESR (mΩ) Example 11 9.9 14 Example 12 9.8 14Example 13 9.8 14 Example 14 9.8 13 Comparative Example 12 9.7 24

As shown in Table 2, in the aluminum solid electrolyte capacitor ofComparative Examples 7 to 11, the conductive polymer layer did not coverthe entire portion where the conductive polymer layer should have beenformed. On the other hand, in the aluminum solid electrolyte capacitorof Examples 11 to 14, the reaction accelerator containing a salt of ananion derived phenolsulfonic acid or cresolsulfonic acid and a divalentor more cation other than a transition metal was used. Accordingly, thepolymerization reaction of 3,4-ethylenedioxythiophene, a monomer, waspromoted. Therefore, the conductive polymer layer could be evenly formedon the entire portion where the conductive polymer layer should havebeen formed, so as to produce good aluminum electrolyte capacitors.Also, the results in Tables 3 and 4 show that aluminum solid electrolytecapacitor in Examples 11 to 14 were excellent in the heat-resistance andthe humidity resistance compared with that in Comparative Example 12.

Furthermore, note that during formation of the conductive polymer layerin Example 14, the ammonium persulfate aqueous solution as an oxidizerwas substituted with an oxidizer dopant solution. The aluminum of solidelectrolyte capacitor of Example 14, in spite of reducing the number ofrepeating times of the polymerization process, was excellent in thevalue of ESR compared with that of Example 11. The results show thateven few number of repeating times of the polymerization process canform an aluminum solid electrolyte capacitor good in its properties.

Evaluation in Tantalum Solid Electrolyte Capacitor Example 15

Tantalum sintered material is immersed in 0.1% phosphoric acid aqueoussolution, while a voltage of 20V was applied to carry out a chemicalconversion treatment to form a dielectric coating. Then, into 0.5%calcium phenolsulfonate aqueous solution prepared in accordance withSynthesis Example 1, the tantalum sintered material was immersed for 1minute, and then it was taken out to dry it at 100° C. for 5 minutes.Then, into 35% 3,4-ethylenedioxythiophene ethanol solution, the tantalumsintered material was immersed for 1 minute, and then it was taken outto keep it at room temperature for 5 minutes. Then, into 35% ammoniumpersulfate aqueous solution, the tantalum sintered material was immersedfor 5 seconds, and then it was taken out to keep it at room temperaturefor 30 minutes to form a conductive polymer layer. Then, the tantalumsintered material having its surface covered with conductive polymerlayer was immersed into pure water for 30 minutes, and then it was takenout to dry it at 70° C. for 30 minutes.

A series of processes from the step of immersing the tantalum sinteredmaterial into the calcium phenolsulfonate aqueous solution to the stepof drying it at 70° C. for 30 minutes was repeated sixteen times. Then,the conductive polymer layer was covered with a carbon paste and asilver paste to prepare a tantalum solid electrolyte capacitor.

Example 16

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l strontium phenolsulfonate aqueous solution (pH6.0) prepared in accordance with Synthesis Example 2 was used. Otherthan that, the same procedure used in Example 15 was used to produce atantalum solid electrolyte capacitor in this example.

Example 17

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l barium phenolsulfonate aqueous solution (pH 6.0)prepared in accordance with Synthesis Example 3 was used. Other thanthat, the same procedure used in Example 15 was used to produce atantalum solid electrolyte capacitor in this example.

Example 18

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l calcium cresolsulfonate aqueous solution (pH 6.0)prepared in accordance with Synthesis Example 4 was used. Other thanthat, the same procedure used in Example 15 was used to produce atantalum solid electrolyte capacitor in this example.

Example 19

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l ethylenediamine phenolsulfonate aqueous solution(pH 5.0) prepared in accordance with Synthesis Example 5 was used andthe temperature of the solution was kept at 60° C. Other than that, thesame procedure used in Example 15 was used to produce a tantalum solidelectrolyte capacitor in this example.

Example 20

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution, asolution (pH 5.0), in which 0.5 mol/l of ethylenediamine phenolsulfonatewas dissolved into 20% ethylenediamine polystyrene phenolsulfonateaqueous solution as prepared in Synthesis Example 6, was used and theaqueous solution was kept at 60° C. Other than that, the same procedureused in Example 15 was used to produce a tantalum solid electrolytecapacitor in this example.

Example 21

Instead of using the 0.5 mol/l calcium phenolsulfonate aqueous solution,a solution (pH 1.5 when diluted into a concentration of 5%), in which0.5 mol/l of ethylenediamine phenolsulfonate was dissolved into 20%ethylenediamine polystyrene phenolsulfonate aqueous solution as preparedin Synthesis Example 7, was used and the aqueous solution was kept at60° C. Other than that, the same procedure used in Example 15 was usedto produce a tantalum solid electrolyte capacitor in this example.

Example 22

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 2-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 wasused, and the number of repeating the polymerization process wasdecreased from 16 times to 10 times. Other than that, the same procedureused in Example 15 was used to produce a tantalum solid electrolytecapacitor in this example.

Example 23

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 2-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 withfurther addition of decyldimethylamineoxide at a concentration of 0.2%was used, and the number of repeating the polymerization process wasdecreased from 16 times to 10 times. Other than that, the same procedureused in Example 15 was used to produce a tantalum solid electrolytecapacitor in this example.

Example 24

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 4-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 withfurther addition of decyldimethylamineoxide at a concentration of 0.2%was used, and the number of repeating the polymerization process wasdecreased from 16 times to 10 times. Other than that, the same procedureused in Example 15 was used to produce a tantalum solid electrolytecapacitor in this example.

Example 25

A tantalum sintered material was prepared in the same manner as Example15 so as to form a dielectric coating. Then, it was immersed into 35%3,4-ethylenedioxythiophene ethanol solution for 1 minute, and then itwas taken out to keep it at room temperature for 5 minutes. Then, intothe same oxidizer dopant solution used in Example 23, the tantalumsintered material was immersed for 5 seconds, and then taken out to keepit for 5 minutes. Then, into the 0.5% calcium phenolsulfonate aqueoussolution (pH 6.0) prepared in accordance with Synthesis Example 1, thetantalum sintered material was immersed for 5 seconds, and then it wastaken out to dry it at room temperature for 30 minutes to form aconductive polymer layer. Then, the tantalum sintered material havingits surface covered with conductive polymer layer was immersed into purewater for 30 minutes, and then it was taken out to dry it at 70° C. for30 minutes.

A series of processes from the step of immersing the tantalum sinteredmaterial into the 3,4-ethylenedioxythiophene ethanol solution to thestep of drying it at 70° C. for 30 minutes was repeated ten times. Then,the conductive polymer layer was covered with a carbon paste and asilver paste to prepare a tantalum solid electrolyte capacitor.

Example 26

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 2-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 wasused, and the number of repeating the polymerization process was reducedfrom 16 times to 10 times. Other than that, the same procedure used inExample 19 was used to produce a tantalum solid electrolyte capacitor inthis example.

Example 27

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 2-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 wasused, and the number of repeating the polymerization process was reducedfrom 16 times to 10 times. Other than that, the same procedure used inExample 20 was used to produce a tantalum solid electrolyte capacitor inthis example.

Example 28

Instead of using 35% ammonium persulfate, an oxidizer dopant solution inwhich 40% ammonium persulfate was mixed with 70% 2-methylimidazolephenolsulfonate aqueous solution (pH 5.0) at a volume ratio of 1:1 wasused, and the number of repeating the polymerization process was reducedfrom 16 times to 10 times. Other than that, the same procedure used inExample 21 was used to produce a tantalum solid electrolyte capacitor inthis example.

Comparative Example 13

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l sodium phenolsulfonate aqueous solution (pH 6.0)was used. Other than that, the same procedure used in Example 15 wasused to produce a tantalum solid electrolyte capacitor in this example.

Comparative Example 14

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l ammonium phenolsulfonate aqueous solution (pH 6.0)was used. Other than that, the same procedure used in Example 15 wasused to produce a tantalum solid electrolyte capacitor in this example.

Comparative Example 15

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/l calcium m-xylenesulfonate aqueous solution (pH6.0) was used. Other than that, the same procedure used in Example 15was used to produce a tantalum solid electrolyte capacitor in thisexample.

Comparative Example 16

Instead of using 0.5 mol/l calcium phenolsulfonate aqueous solution inExample 15, 0.5 mol/1 magnesium m-xylenesulfonate aqueous solution (pH6.0) was used. Other than that, the same procedure used in Example 15was used to produce a tantalum solid electrolyte capacitor in thisexample.

Comparative Example 17

40% butanol solution of ferric p-toluenesulfonate was mixed with3,4-ethylenedioxythiophene at a mass ratio of 4:1, and the mixture wasstrongly shaken for 10 seconds. Into this mixture, the same tantalumsintered material (that is, the tantalum sintered material having formeda dielectric coating) as used in Example 15 was immersed quickly for 5seconds, which was then taken out. The tantalum sintered material waskept for 30 minutes at room temperature and then it was immersed in purewater for 30 minutes. Then, the tantalum sintered material was taken outand dried for 30 minutes at 50° C.

The sequential process from the step of immersing the tantalum sinteredmaterial into the mixture of the ferric p-toluenesulfonate butanolsolution and 3,4-ethylenedioxythiophene to the step of drying at 50° C.for 30 minutes was repeated five times to form a conductive polymerlayer on the surface of the tantalum sintered material. Then, theconductive polymer layer was covered with a carbon paste and a silverpaste to prepare a tantalum solid electrolyte capacitor.

As to the tantalum solid electrolyte capacitor of Examples 15 to 28 andComparative Examples 13 to 17, the capacitance and ESR were measured inthe same manner as described in connection with the aluminum solidelectrolyte capacitor. The results are listed in Table 5 below. Theresults in Table 5 were obtained as follows: each of capacitance and ESRwas measured at 10 points, from which an averaged value was calculatedwhile rounding off the decimal points.

TABLE 5 Capacitance (μF) ESR (mΩ) Example 15 110 34 Example 16 109 35Example 17 106 36 Example 18 104 35 Example 19 103 39 Example 20 105 38Example 21 103 37 Example 22 105 35 Example 23 110 33 Example 24 110 33Example 25 108 33 Example 26 111 34 Example 27 109 34 Example 28 108 32Comparative Example 13 (*3) (*3) Comparative Example 14 (*3) (*3)Comparative Example 15 (*3) (*3) Comparative Example 16 (*3) (*3)Comparative Example 17 108 34 Note that in Table 5, the mark (*3)indicates that the conductive polymer layer could not coat the whole ofthe surface of the tantalum sintered material so that the capacitanceand the ESR were not measured.

Five samples were arbitrarily selected from good samples of the tantalumsolid electrolyte capacitor of Examples 15 to 28 and Comparative Example17. They were kept at 125° C. for 500 hours, and then, capacitance andESR were measured in the same manner as described above. The results arelisted in Table 6 below. The results in Table 6 were obtained asfollows: each of capacitance and ESR was measured at 5 points, fromwhich an averaged value was calculated with rounding off the decimalpoints.

TABLE 6 Capacitance (μF) ESR (mΩ) Example 15 106 37 Example 16 105 38Example 17 103 40 Example 18 100 40 Example 19 100 42 Example 20 102 42Example 21 100 40 Example 22 102 38 Example 23 107 36 Example 24 106 36Example 25 105 36 Example 26 106 37 Example 27 105 38 Example 28 103 35Comparative Example 17 103 75

Furthermore, another sets of five samples were arbitrarily selected fromgood samples of the tantalum solid electrolyte capacitors of Examples 15to 28 and Comparative Example 17. They were kept at an environment of85° C. and 85% RH for 1000 hours, and then capacitance and ESR weremeasured in the same manner as described above. The results are listedin Table 7 below. The results in Table 7 were obtained as follows: eachof capacitance and ESR was measured at 5 points, from which an averagedvalue was calculated with rounding off the decimal points.

TABLE 7 Capacitance (μF) ESR (mΩ) Example 15 108 36 Example 16 107 36Example 17 105 38 Example 18 103 38 Example 19 107 40 Example 20 107 40Example 21 105 39 Example 22 104 37 Example 23 109 35 Example 24 109 35Example 25 106 35 Example 26 107 35 Example 27 107 35 Example 28 105 33Comparative Example 17 107 65

As shown in Table 5, in the tantalum solid electrolyte capacitor ofComparative Examples 13 to 16, the surface of the tantalum sinteredmaterial of the element was not covered with the conductive polymerlayer. On the other hand, in the tantalum solid electrolyte capacitor ofExamples 15 to 28, the reaction accelerator containing a salt of ananion derived from phenolsulfonic acid or cresolsulfonic acid and adivalent or more cation other than a transition metal was used.Accordingly, the polymerization reaction of 3,4-ethylenedioxythiophene,a monomer, was promoted. Therefore, the surface of the tantalum sinteredmaterial of the element could be evenly covered with the conductivepolymer layer, so as to produce good tantalum electrolyte capacitors.

Moreover, the results in Example 15 and 22 to 24 using the same reactionaccelerator, that is, calcium phenolsulfonate, are compared as follow:In Examples 22 to 24, instead of using an ammonium persulfate solutionas an oxidizer solution, an oxidizer dopant solution including aconductive polymer polymerization dopant such as 2-methylimidazolephenolsulfonate and 4-methylimidazole phenolsulfonate was used. Theconductive polymers in Examples 22-24 formed good tantalum solidelectrolyte capacitor, compared with Example 15 in which the oxidizersolution did not include the dopant, in spite of few number of repeatingthe polymerization process. The effects by using the reactionaccelerator together with the oxidizer dopant solution including adopant were shown in these examples.

Similarly, a comparison was made between the results of Examples 26 and19 (both using ethylenediamine phenolsulfonate as a reactionaccelerator); the results of Examples 27 and 20 (both using a solution(pH 5) in which ethylenediamine phenolsulfonate was dissolved into 20%ethylenediamine polystyrene phenolsulfonate aqueous solution as areaction accelerator); and the results of Examples 28 and 21 (using asolution (pH 1.5 when diluted into a concentration of 5%) in whichethylenediamine phenolsulfonate was dissolved into 20% ethylenediaminepolystyrene phenolsulfonate aqueous solution). The number of repeatingpolymerization in Example 26 was fewer than that in Example 19; thenumber of repeating polymerization in Example 27 was fewer than that inExample 20; and the number of repeating polymerization in Example 28 wasfewer than those in Example 21. Nonetheless, the conductive polymers inExamples 26-28 formed good tantalum solid electrolyte capacitor.Accordingly, the results show the effects in using the reactionaccelerator in addition to the oxidizer dopant solution. Also, theresults in Tables 6 and 7 show that the tantalum solid electrolytecapacitors in accordance with Examples 15 to 28 were better inheat-resistance and humidity-resistance than that in Comparative Example17.

INDUSTRIAL APPLICABILITY

As explained above, the present invention provides a reactionaccelerator which can promote the polymerization reaction of the monomerin producing a conductive polymer having a high electric conductivity.Also, according to the present invention, the use of the reactionaccelerator can produce a conductive polymer having a high electricconductivity as well as heat-resistance. The use of the conductivepolymer as a solid electrolyte can produce a solid electrolyte capacitorreliable over a long period of time.

1. A reaction accelerator for polymerizing conductive polymer,comprising: a salt of an anion derived from a sulfonic acid having askeleton of benzene or naphthalene having at least one OH group, and atleast one divalent or more cation other than a transition metal cation.2. A reaction accelerator for polymerizing conductive polymer accordingto claim 1, wherein the salt is in an aqueous solution.
 3. A reactionaccelerator for polymerizing conductive polymer according to claim 1,wherein the reaction accelerator in an aqueous solution having aconcentration of 5 mass % has a pH of 1 or more.
 4. A reactionaccelerator for polymerizing conductive polymer according to claim 1,wherein the salt is one from phenol sulfonic acid or cresol sulfonicacid.
 5. A reaction accelerator for polymerizing conductive polymeraccording to claim 1, wherein said divalent or more cation is selectedfrom the group consisting of calcium ion, strontium ion, barium ion,aluminum ion and ethylenediamine ion.
 6. A conductive polymer having amatrix including a salt of an anion derived from a sulfonic acid havinga skeleton of benzene or naphthalene having at least one OH group, andat least one divalent or more cation other than a transition metalcation.
 7. A conductive polymer according to claim 6, wherein the matrixof the conductive polymer is a polymer of at least one monomer selectedfrom the group consisting of thiophene, pyrrole, aniline and derivativesthereof.
 8. A conductive polymer according to claim 6, wherein the saltis one from phenol sulfonic acid or cresol sulfonic acid.
 9. Aconductive polymer according to claim 6, wherein said divalent or morecation is selected from the group consisting of calcium ion, strontiumion, barium ion, aluminum ion and ethylenediamine ion.
 10. A conductivepolymer according to claim 6, wherein said divalent or more cation isincluded at a concentration of 10 to 1000 ppm.
 11. A conductive polymeraccording to claim 6, wherein the conductive polymer is obtained bychemical oxidation polymerization of a monomer by using a persulfatesalt and the reaction accelerator for polymerizing conductive polymer.12. A conductive polymer according to claim 6, wherein the conductivepolymer is obtained by chemical oxidation polymerization of a monomer byusing an oxidizer dopant solution and the reaction accelerator, whereinthe oxidizer dopant solution comprises a mixture of a persulfate saltwith an alkylamine salt or imidazole salt of an anion derived from asulfonic acid having a skeleton of benzene or naphthalene having atleast one OH group and at least one sulfonate group, and at least onedivalent or more cation other than a transition metal cation.
 13. Asolid electrolyte capacitor including a solid electrolyte of theconductive polymer according to claim 6.